On 21^st June, the Sun

The correct answer is: does not set below the horizon at the Arctic Circle.

Explanation:

On 21^st June, known as the Summer Solstice in the Northern Hemisphere, the Earth's Northern Axis is tilted directly towards the Sun. On this day, the Sun is vertically overhead at the Tropic of Cancer (23.5° N latitude).

Because of this maximum tilt toward the Sun, the entire region north of the Arctic Circle (66.5° N latitude) experiences 24 hours of continuous daylight. Consequently, the Sun does not set below the horizon at the Arctic Circle on 21^st June (often referred to as the "Midnight Sun").

Let's evaluate the other options for clarity:

• Does not set below the horizon at Antarctic Circle: Incorrect. The Antarctic Circle experiences 24 hours of night/darkness on 21^st June.

• Shines vertically overhead at noon on the Equator: Incorrect. The Sun shines vertically overhead at the Equator during the equinoxes (21^st March and 23^rd September).

• Shines vertically overhead at the Tropic of Capricorn: Incorrect. The Sun shines vertically overhead at the Tropic of Capricorn during the Winter Solstice in the Northern Hemisphere (22^nd December).